Due to CO2's superior "compressibility", CO2 Brayton is apt to be both more efficient & cheaper to build (smaller) than an open-air system which, in turn, should translate to lower cost electricity. It also provides another barrier to tritium loss. I'm not too excited about generating another customer for "fracked" natural gas.

As far as recycling the 7Li is concerned I just feel that it wouldn't be worth doing as far as the utility's owners are concerned. In any case, recovering it would probably be easier/cheaper after the glass logs containing it along with that scenario's discarded thorium have cooled off in the repository (it ain't gonna go anywhere).

I see the technical advantage of the CO2 Brayton, I'm just worried about the separate development work & associated risk. As long as someone else is funding it and a demonstration is built, no worries. The NACC is compelling primarily because of the minimal development work required (everyone loves off the shelf sourcing); at the same time I think the natural gas co-firing is underrated. ugh bad policy, a lot of markets have (or will have) grids with extreme load transients...and I expect tripling power output in an MSFR or other reactor in the course of an hour will do bad things to system life; if that's the case, the natural gas is going to be used for peaking power anyway, you may as well increase it's combustion efficiency.

Alternatively I suppose you could overbuild reactor capacity and use cogeneration or desalination when loads are lower. That's a more appealing setup, but you lose some siting flexibility.

Thermodynamic calculations suggest that SiC won't work in MSRs (but may in FHRs) because U and lots of different FP form weaker bonds to fluoride than does the silicon in SiC. This means that the stuff in such dirty "FLiBe" etc. will tend to corrode SiC to form "dirt" carbides & SiF4.

This stuff is timely because even DOE is beginning to realize that its approach to promoting/developing a nuclear renaissance doesn't work. Wednesday's Post Register (IF's local newspaper) had an article describing how INL is trying to "kick start nuclear brainstorm sessions". I'd sent copies of the paper* I've just written to three of my ex-INL colleagues that same day & got call backs from two of them. Both now want to "help".

ASME's paper screeners bitched about its cut & pastes but have since decided (this morning) that they still want it so I've made some changes. (ATTACHED)

The one thing that sort of knocked me in the face was your section about the Red Book uranium reserves. I'd just like to point out that this is not the actual amount of uranium out there. The Red Book's reserves are all bigger today than they were in years past. How can you have a pie, eat it, and end up with two pies after? Because you didn't bother to look for other pies. So it is with uranium. We can look at how many pies you have in your refrigerator, or we can look at the yearly production of pies. Or we can look at the raw ingredients needed to make pies and conclude that we can make many more if we want to. I don't know why I am talking about pies I must be hungry.

Here's the estimate of the actual amount of uranium in the earth's crust

Guys, having spent some more time in the public relations "trenches" in the last few weeks, let me relate to you that the size of uranium reserves has nothing to do with public acceptance of the technology. The public believes that reactors take something best left alone (uranium) and turn it into a horrible monster that will come and devour their children in their sleep. From that perspective, telling them that there is plenty of that somewhat horrible stuff (uranium) that can be turned into devouring monsters by a fleet of nuclear reactors offers them pretty much zero comfort.

On the other hand, a vision of benign solar panels and gently spinning wind turbines is offered to them as the alternative, and they imagine, oh yes, I could see a few of those on the outskirts of where I live and I can imagine one or two panels on the roof I don't care about, and if I have those two wonderful things then the horrible devouring monster can never eat my children.

It's a fantasy of course, but I would wager about 98% of people believe some minor variant of this.

I've gone around & around on the "uranium availability" (fuel cost) issue in the EFT topic describing the evolution of my MSFR concept/paper & don't want to rehash it here/again. I can tell you though that it does make sense to both laypersons & the people who decide what kind of reactors they should buy.

Kirk

I agree that the possibility of implementing a nuclear renaissance without the uranium boogeyman is apt to be attractive to lots of folks.

Guys, having spent some more time in the public relations "trenches" in the last few weeks, let me relate to you that the size of uranium reserves has nothing to do with public acceptance of the technology. The public believes that reactors take something best left alone (uranium) and turn it into a horrible monster that will come and devour their children in their sleep. From that perspective, telling them that there is plenty of that somewhat horrible stuff (uranium) that can be turned into devouring monsters by a fleet of nuclear reactors offers them pretty much zero comfort.

So glad that some people here are finally getting it !

Canada supplies a good deal of the world's uranium -- including to the United States.That's great, because it means that Canada's product is helping to reduce coal use south of the border -- which means less pollution getting blown north, back into Canada, polluting our air and water with nasty stuff like Mercury.

The funny part is that there are many activists in Canada opposing uranium mining -- with exactly the attitude described by Kirk.

Moreover, some of these activists travel to the US to scare our neighbors into opposing nuclear power.Just as one example, here is an info-graphic about a member of the Green Party of Canada who traveled to Vermont a couple of years ago, in order to help local activists shut down Vermont Yankee NPP (which they eventually succeeded, as you know).

The gist of the GPC candidate's narrative is that nuclear power is dirty & dangerous, because uranium mining is dirty & dangerous.

However, it seems to me that an argument that predicates desirability of breeder reactors on an agreement with the the Greens that uranium mining is dirty & dangerous, is just about equally misleading and worthy of debunking.

The uranium mining industry in Canada is regulated by the Canadian Nuclear Safety Commission (CNSC), as indicated in the link at the bottom of my info-graphic, and as such is considerably safer than any other mining industry in this country.Typically, when other countries consider getting into uranium mining, they send safety specialists to Canada to learn about how it's done properly.

Thermodynamic calculations suggest that SiC won't work in MSRs (but may in FHRs) because U and lots of different FP form weaker bonds to fluoride than does the silicon in SiC. This means that the stuff in such dirty "FLiBe" etc. will tend to corrode SiC to form "dirt" carbides & SiF4.

I've done some thinking about what a MOSEL might actually be made of. While both EVOL & their Russian MOSART colleagues seem to have already picked some promising candidates (which are both probably pretty similar to Hastelloy N), it seems to me that relatively cheap HT9- type steel might also work fine if over plated with a thin layer of pure nickel.

This idea's attractive features include1) HT9 cladding has proven to be extremely durable (doesn't swell & therefore retains its strength) under extremely high fast neutron irradiation doses (that's why Terrapower is "studying" it for their super high burn-up LMFB(almost)R see http://terrapower.com/uploads/docs/HT9_ ... eactor.pdf )2) it should be much cheaper than Hastelloy N (very little nickel, Mo, or W - mostly just Fe with about 10% Cr)3) there's already a good deal of fabrication experience 4) HT9 cladding would probably absorb fewer otherwise useful neutrons than would Hastelloy N5) in this case, the nickel wouldnt have to contribute to the part's strength - it's just there to resist corrosion

This suggests that it'd make sense for someone at DOE to fund studies of 1) how best to go about nickel plating complex HT9 reactor parts (e.g., a MOSEL's core HX) & 2) how resistant such layers would be to flaking off under realistic operational conditions.

Incidentally, in real MSR salt streams pure Mo reactor parts wouldn't work because the UF4 in them would oxidize the Mo to MoF2.

(next morning) re this post: I've just been told by people who ought to know at UCBerkeley that HT9 gets too weak at Ts>600 C to use for this purpose & that nickel wouldn't stick to it anyway.

_________________Darryl Siemer

Last edited by darryl siemer on Mar 08, 2015 1:12 pm, edited 2 times in total.

I have always been worried about two of the problems with LFTR concepts.1 99.995% Li-7 required for FLiBe. It will take a long time and high cost to manage.2. Graphite moderator. It increases the core size by one order of magnitude. It has to be 80-90% graphite. It increases the cost too.Now the construction material raise another intractable problem. The solution for a thorium fueled reactor seems to require1. A calandria design like the CANDU.2. A Th-Pu(RG) or Th-20%LEU solid fuel with a high burn up.3. Heavy water moderator. It can be constantly cooled to avoid vaporization.4. A low vapor pressure coolant like a high boiling hydrocarbon or fluorocarbon. I had earlier suggested the Krytox lubricant but now Dow-therm heat transfer fluid has come to notice.5. A thorium blanket. A metallic thorium blanket could be easily reprocessed by electrolysis. The irradiation period could be optimized for maximum U-233 production.

What I gather from them is that modern material science theory suggests that the best stuff to make MSR heat exchangers, pipes, etc of is apt to be a Ni-based alloy similar to the Hastelloy N that ORNL's workers assumed for most of their reactors

I see the technical advantage of the CO2 Brayton, I'm just worried about the separate development work & associated risk. As long as someone else is funding it and a demonstration is built, no worries. The NACC is compelling primarily because of the minimal development work required (everyone loves off the shelf sourcing); at the same time I think the natural gas co-firing is underrated. ugh bad policy, a lot of markets have (or will have) grids with extreme load transients...and I expect tripling power output in an MSFR or other reactor in the course of an hour will do bad things to system life; if that's the case, the natural gas is going to be used for peaking power anyway, you may as well increase it's combustion efficiency.

Alternatively I suppose you could overbuild reactor capacity and use cogeneration or desalination when loads are lower. That's a more appealing setup, but you lose some siting flexibility.

Regarding CO2 brayton "separate development work": that's why I've chided DOE about the rate at which it "studies" stuff relevant to implementing any sort of efficient nuclear renaissance. The sad fact of the matter is that just about everything DOE does in that arena has become a jobs program which incentivizes both managers and researchers to keep everything going for as long as possible.

Regarding "overbuilding": I'm absolutely convinced that as soon as clean electricity becomes cheap enough, thousands of clever apps will suddenly be invented to use whatever "excess power" is produced (fuel/ammonia production, car battery charging, houses with built in, LED lit, greenhouses, etc. - heck, we could even start making most of the stuff we're now importing from China/Korea for ourselves again.)

The MOSEL concept's Achilles heel is that the nickel-based superalloys invoked for both it and ORNL’s MSBR are unlikely to be sufficiently durable. The reason for this is that unlike MSFR or MSBR, it would put that metal in the center of the core where the neutron flux is far higher than at its periphery. If that flux is similar to that predicted at the center of MSFR’s core (roughly 8E+15 n/cm2/s, see Fig. 6.5 of Fiorina's thesis (https://www.politesi.polimi.it/bitstrea ... iorina.pdf), Figs. 2 and 4 of Delpech et als' s paper (https://inis.iaea.org/search/search.asp ... N:43002322 ) suggest that a nickel-based core HX would only last for about 5 months.

This means that unless its core HX could be made of 58Ni-free "Hastelloy" or corrosion protected (plated) Mo sheet metal (something else?), it's unlikely to be practical.

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